This project was performed in conjunction with Dr. Richard Jackson (Harvard University) and Drs. Eisenbarth and Chase (University of Colorado). The project was originally conceived as a randomized, double blind, placebo controlled trial of parenterally administered insulin (placebo, IV, SC or IV and SC) to prevent or delay the development of IDDM in the first degree relatives of patients with IDDM who are at high risk to develop IDDM. With the development and initiation of the National Diabetes Prevention Trial (see project #442: "Diabetes Prevention Trial-1" ) enrollment in this project was discontinued. Prior to discontinuation 1 subject was enrolled in Cincinnati. This subject remained in the study until October 1997 when an oral glucose tolerance test revealed that she had IDDM. Prior to entry into the protocol, she was predicted to develop IDDM in 18 months. Her actual time to the development of IDDM was 52 months. She received daily SC insulin during the protocol. The protocol has been closed in Cincinnati. The protocol remains active in Boston and Denver.